1. Field of the Invention
The present invention relates to a swash plate compressor of an open type which is operated by an outside drive force source. The present invention can be suitably used for a refrigerating system using a LO refrigerant at a high operating pressure, such as carbon dioxide (CO.sub.2).
2. Description of the Related Art
A swash plate type compressor is known having a swash plate arranged obliquely with reference to an axis of a rotating shaft. A rotating movement of the swash plate cause pistons to be axially reciprocated. A volume of an operating chamber on one side of the piston is increased during an intake stroke of the piston and decreased during an exhaust stroke of the piston. Thus, during the intake stroke, the refrigerant is sucked into the operation chamber, while, during the exhaust stroke, the refrigerant is discharged from the operating chamber.
An axial thrust force is generated in the swash plate, which is transmitted to the rotating shaft. Thus, thrust bearings for receiving the thrust force are arranged between faced axial surfaces of a boss portion of the swash plate and a housing.
As the refrigerant, a freon has been conventionally used. However the use of freon has been restricted. Thus, the inventors have recently studied carbon dioxide (CO.sub.2) as a refrigerant for executing a refrigerating cycle. During such a study, the inventors have found that the use of carbon dioxide as a refrigerant causes the service life of the thrust bearing to be highly reduced when compared with a service life of the thrust bearing when the freon is used as a refrigerant.
In view of this, tests regarding the service life of thrust bearings have been conducted by the inventors. From these test, it has been found that an axial force is generated in the rotating shaft of the compressor for a kinematic connection to the outside rotating source due to a difference between an atmospheric pressure and a pressure inside a chamber for storing the swash plate, which corresponds to a pressure to the refrigerant sucked into the compressor. This pressure difference between the outside pressure and the inside pressure is highly increased in the refrigerating system using carbon dioxide as the refrigerant due to an increased intake pressure, which is as high as 35 kgf/cm.sup.2 over the conventional system using the freon. As a result, a load as generated in the thrust bearing is also greatly increased, which causes the service life of the thrust bearing to be highly shortened. According to a calculation by the inventors, the conventional refrigerating system using freon (of intake pressure of 2 kgf/cm.sup.2) generates a thrust force of about 10 kgf, while the refrigerating system using the carbon dioxide generates a thrust force of 200 kgf. This means that a highly increased thrust force is generated in the thrust bearings in the refrigerating system using the carbon dioxide compared to the refrigerating system using freon.